In the related art, in order to reduce the oil consumption of a vehicle and improving the Noise, Vibration and Harshness (NVH) properties of the vehicle, a neutral gear control function of an automatic transmission is provided on more and more vehicles; an automatic Transmission Control Unit (TCU) may control a linear pressure sensor inside the transmission, so that the vehicle to keep at a Drive (D) gear (forward gear); when a driver stamps on a brake and a pressure of a brake main cylinder reaches to a certain value, the automatic transmission is in a neutral state and the power output of an engine is disconnected; and when the driver loosens the brake, the pressure of the brake main cylinder is close to 0 kpa and no longer meets the requirement on neutral gear control in the automatic TCU at this moment, then the neutral gear control is exited.
In order to improve the driving comfort of the vehicle, more and more vehicles are provided with an autohold function. The autohold function refers to that an Electrical Park Brake (EPB) directly brakes a wheel by changing a wheel cylinder pressure in combination with an Electronic Stability Program (ESP). When the driver brakes the vehicle, the autohold function brakes the wheel in terms of a brake requirement of the driver; at this moment, the driver may loosen the brake pedal and the vehicle still automatically keeps stationary, so that a right foot of the driver is liberated. When the system detects a start intention of the driver, for example when the driver stamps on an accelerator, the brake is relieved automatically. This function can guarantee the comfort of starting the vehicle when the brake is automatically relieved and may actively boost the pressure to keep the vehicle stationary when a brake force is insufficient.
In the related art, the neutral gear control function of the automatic transmission and the autohold function are increasingly and widely applied to the vehicle. However, when the two functions exist, simultaneously, an incompatible condition may be occurred with the following reasons.
First, when the driver stamps on the brake pedal at the D rear, the autohold function and the neutral gear control function of the automatic transmission are activated simultaneously. However, the autohold function is designed to relieve the right foot of the driver and improve the driving comfort of the driver. If the driver loosens the brake pedal, the autohold function still keeps the wheel to be braked, the neutral gear control function is exited and the engine outputs a power outward. At this moment, the neutral gear control function can no longer improve the oil consumption and the NVH properties of the vehicle.
Second, when the neutral gear control function is exited, since the engine outputs the power outward, the vehicle has a driving tendency. However, at this moment, the autohold function brakes the wheel to make the vehicle stationary. In this way, the vibration of the vehicle is increased, the comfortable capability becomes poor, and additionally, the oil consumption is also increased.